Leaves are now smothering the player and mobs that move/spawn inside them, causing suffocation damage. This is both annoying and unrealistic, and needs to be taken out immediately:
1) Sticking your face in a bush or tree's foliage does not suffocate you IRL, and so you nor your animals (horses, livestock, etc) nor any other mob that spawns with their head in a leaf block should smother either.
2) Standing next to a sapling when it "grows" instantly into a tree can be often fatal in-game, for you or any mob.
3) Riding your saddled animal through a forest or jungle is now more of a lethal prospect than just an annoyance of navigating around/over them.
4) You and your livestock and other mobs that hop or jump up into a leaf block (on hillsides, etc) will start to suffocate immediately.
I ask that this suffocation be disabled ASAP for general gameplay balance and "fun" factor. Perhaps leaving it in on "Hard" mode is possibly feasible, but document appropriately.